This invention relates to a strainer locking assembly for a digester vessel and constitutes an improvement on co-owned U.S. Pat. Nos. 2,163,437; 2,852,369 and 4,040,901.
In the manufacture of most types of pulp, with which to make paper or board, from wood particles, the wood particles are initially subjected to chemical action at elevated pressure and temperature. This process is known in the pulp-making trade as "digesting", and takes place in pressure vessels known as "digesters". The process may be accomplished by filling the digester with wood particles and closing the digester while the process takes place, known as "batch digesting", or may be accomplished by continuously filling the digester with wood particles while simultaneously removing processed material, known as "continuous digesting".
In any of these instances, the process chemicals are added to the digester vessel as an aqueous solution and water is contained in the wood particles, so the digester vessel is essentially filled with water containing process chemicals or chemicals dissolved from the wood particles, known as "liquor".
Frequently during the digesting process, it is desired to remove part of the liquor from the digester vessel, usually accomplished by allowing the liquor to flow through screened openings to outlet pipes. The screens covering the outlet openings allow the liquor to flow, but prevent the wood particles from leaving the vessel with the liquor.
The screens, i.e., strainer panels, over the outlet openings may be circular, rectangular or in the form of a horizontal ring around the inside circumference of the digester vessel. The ring is frequently made up from a number of abutting sections of screen mounted on frames for mechanical support and for attachment to the digester vessel wall. In practice, these screen sections may have to be removed and replaced periodically, i.e., for cleaning or maintenance, so it is desirable to have means of securing the screen sections in place in the digester vessel which is simple and easy to operate, highly reliable and inexpensive to make or use.
A number of disadvantages or defects have characterized the prior art expedients for securing the strainer panels or screen sections in place. In some instances these came loose unintentionally. In other instances the locking or securing devices were not simple and easy to use--more particularly, they could be installed correctly. In many instances threaded fasteners were employed which could corrode or gall. In other instances the components of the lock were not sturdy and could be broken during installation or removal. All of these are avoided according to the instant invention which has an additional significant advantage of being disassembable for ready removal of strainer panels merely through the use of a pry bar and hammer. According to the invention, a socket member is provided between each pair of perimetrically related panels and is contoured so as to support the same. The socket member is equipped with a recess for wedgingly receiving both a clamp block member and a lock member which cooperate in both releasably maintaining each other in place within the socket recess and at the same time releasably clamping the adjacent strainer panels.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.